Centuri Hummingbird Boost Glider simulation
 

Attached is a simulation I made for the Centuri Hummingbird Boost Glider, Centuri Catalog Number KF-2. You will also need to down load and install the attached dart motor file to get the simulations to run properly.

Attached is a picture of this kit that I recently built.

:cool: I've downloaded this one at several times over the past twenty years, but I never got around to building one. It would fit in nicely with my current fleet of "gliders". :rolleyes:

I used a technique I have been experimenting with to construct the fiberboard parts for the Hummingbird. I glued two sheets of poster board and a printout of all the parts on high quality bond paper together using a spray adhesive. I cut out the parts from this 3 ply stack. I used rubber cement thinner (heptane) to clean up any glue overspray. I think the technique worked out nicely for this model. In my hands, the spray adhesive seems to work better than sticker paper for fastening the artwork to the 2 ply's of poster board.

I also built a Centuri X-24 Bug (see attached picture) but I haven't yet figured out how to get the Rocksim program to provide an acceptable simulation. For the X-24 simulation, I have been trying to simulate the flight as a boosted dart (like I did for the Centuri Hummingbird) so I can account for the motor ejection. That is not the problem; it seems Rocksim distorts the fins when I try to put them on a conical transition. Everything works fine when I simulate the model using a regular body tube.

There are other tools than Rocksim.

http://www.v-serv.com/crp/software.htm

Jerry,

Wow, thanks, I didn't know about these software packages! I typically use RockSim, Open Rocket and VCP. I also have some old CFD programs from Aerorocket that I occasionally use when I want to look at rocket's coefficient of drag. Can these software packages handle odd-ball designs like tube fins, ring fins, square body tubes and unsymmetrical fin designs?

I love the Hummingbird. Picked up an already built one in a shop in something like 1979. Loved it. Don't recall when I lost it.

I've built BT20, BT50 and BT60 sizes. The BT60 size ejected the motor pod and had airfoiled wings. It power pranged - I should get around to repairing it.

They fly like described in the Holverson kits. Arch overhead in a backwards loop and pop the motor about when it come level again. They don't usually glide a long way, but my BT20 size caught a perfect glide and literally flew off into the sunset.

Someday I want to mod a Stratoblaster kit into a giant Hummingbird

I probably should have posted this screen capture from the RockSim file I created for the Centuri Hummingbird. It shows all the details and even the expected altitudes for a few motors.

If I'm not mistaken eRocket is working on making a kit of this glider.

Wolf,

I liked watching the one backwards loop this model makes before it stalls and hits the ground. My brothers put a C motor in the original kit I built while I was away at school and didn't find/recover it.

I certainly hope so! If answering this wouldn't betray any confidences, will it be a true "Repro-Retro" kit that uses the #7 (ST-7, 0.759" Outside Diameter) Centuri tubing and a balsa duplicate of the Centuri PNC-70 nose cone? Such a kit could use not only 18 mm motors, but also 13 mm mini motors (in a streamer-recovered motor adapter mount). Also:

It might be possible to minimize or even eliminate the backward loop (which occurs under power, after launch) by using a 13 mm motor adapter mount whose #5/BT-5 mini motor mount tube is located off-center by using suitably-punched (or laser-cut) flat fiber centering discs. (The rear-ejected, streamer-recovered motor mount of the Centuri Space Shuttle kit [it can be seen here: http://www.ninfinger.org/rockets/no...a/72cen044.html ] had such an off-center motor mount tube.) Installing such a 13 mm motor adapter mount in the Hummingbird with the motor mount tube on the "bottom" would lower the motor's thrust line (the adapter discs could even have their motor mount tube holes arranged to give a slightly "pitch down" thrust vector, if desired) and could prevent the backward loop under power (the Jetex, Jet-X, and Rapier model jets used/use similar thrust line pointing for the same reason).

I flew my Centuri Hummingbird clone yesterday at the Wright Stuff Rocketeers (WSR #703) launch on their Rip Rap Road field in Dayton, OH. The winds at he launch were about 5 mph and the temperature was around 82 degrees F, pretty decent weather for glider flights! I test flew (hand tossed) and trimmed the glider at the launch site before its flight. I chose to use an A8-3 motor because I thought my build was on the heavier side due to the clear-coat finish I applied. I also taped a 2" wide x 10 inch long crepe paper streamer to the motor so it would come down on a recovery device. The boost was pretty much straight up, probably close to the 375 feet AGL as RockSim predicted. The motor ejected near apogee and the glide phase was upright. However, the crepe paper streamer on the motor tore in half and the free part of it got caught on the Hummingbirds rear stabilizer. I am not sure if this helped put the glider in an upright position. I recovered the Hummingbird glider about 300 feet from the launch pad with some slight charring and a 6 inch piece of crepe paper caught on the rear stabilizer. I estimated the glide time was around 20 seconds the glider made at least three complete horizontal loops during its decent. I did not get a chance to fly the Hummingbird again, because there were a lot of other rockets I wanted to fly (Centuri X-24 bug being one of them).

I also visited eRockets, and Randy Boadway, the owner, confirmed the company's interest in releasing a Semroc reproduction of the Centuri Hummingbird glider. I gave Randy several Hummingbird nosecones that I 3D printed for ST-7 tubing (in PLA and ABS plastic) but found out they were too loose of a fit to be of any use. I plan on designing and printing a better fitting 1.5 inch ogive nosecones for the ST-7 tubing.

That's pretty funny, Bruce. I just came into the thread to tell you that someone flew one at our launch yesterday. Good to put a face to the YORF name.

Bill,

Sorry I didn't introduce myself. It was kind of a busy launch for me between the kids from the build session in the morning, the heat in the afternoon, the launch controller failures, and all the rockets I wanted to fly! I did join WSR and was wondering if there are pictures from the launch posted somewhere? It would be nice to see the launch or even flight pictures of my Hummingbird or X-24 Bug as well as some of my friend Andrew's mid power flights. Did you get a chance to see the nosecones I gave to Randy?

Nope, I was busy like you were. I have a shot of the Hummingbird igniting, but my new camera is pretty slow in burst mode, so that's all I got. I'll post it when I get home in the morning. The X-24 Bug finally left the pad and all I got there was the smoke trail. I've got tons of shots of it sitting on the pad. ;) That was one stubborn bird.

Will you be selling those 3D printed #7 nose cones, by any chance? I'd love to use those in the Semroc "Retro-Repro" Hummingbird B/Gs, and I imagine other folks would, too (plus they could be used in Centuri Moonraker kit clones).

I have plans to offer the 3D printed nosecones to eRockts to use in their remake of the Centuri Hummingbird boost glider kit. I looked at the Centuri Moonraker build on Chris Michielssen's blog: http://modelrocketbuilding.blogspot...ild-part-1.html , and now I am not sure I got the shape exactly right. I printed the shape as elliptical and made it match to the profile tracing from: https://sites.google.com/site/centurihummingbird/

Can some one provide exact measurements and/or a good close-up profile of this nosecone next to a standard measuring scale (ruler) of some sort?

The best thing about 3D printer is that I can easily change the print color so a red, white or blue #7 nosecones are possible. I adjusted my 3D print file so the nose cone fits in the ST-7 tubing that I got from eRockets. I made the nosecone shoulder slightly loose to accommodate the sticker or pressure sensitive tab, as supplied in the original kit, which was used for gluing the nosecone into the paper body tube.

I can easily make decent 3D prints in PLA of the current design. I already have printed a half dozen or so in white and blue PLA. I am worried that the PLA plastic will not be durable enough for this purpose. I have read stories about PLA prints melting in a hot car parked in the sun or shattering when dropped on a hard surface on a cold day when the temperature is below freezing. These nose cones weigh in at 3.1 +/- 0.05 grams I am wondering if that is too heavy for the boost glider?

My ABS prints are much smoother than the PLA prints and should be much more durable and they weigh less at 2.8 +/- 0.05 grams. I currently have about a half dozen white ones since I only have this color of ABS filament.

I have--packed away somewhere [*argh*]--a cast polyurethane resin duplicate of the Hummingbird and Moonraker #7 plastic nose cone. This is the PNC-70, whose total length (not counting the tenon [shoulder] that fits inside the body tube) is 1.5 " (see: http://www.ninfinger.org/rockets/no...a/80cen036.html ). Also:

The PNC-70 isn't an elliptical nose cone (the one on the Hummingbird clone in your second link above [*not* Chris Michielssen's blog]) is a hand-carved elliptical nose, made from a balsa block (as listed in its parts list). The PNC-70, shown in the Moonraker kit photograph on Chris Michielssen's blog, is a tangent ogive nose cone with a rounded tip (knowing its length, 1.5", maybe the picture on Chris Michielssen's blog could be of some help?). I can "bracket," to an extent, the PNC-70's shape for you:

The PNC-70 nose cone's base diameter--which is the same as the #7 body tube's outside diameter--is 0.759" (the #7 body tube's ^inside^ diameter is 0.715", see: http://www.ninfinger.org/rockets/no...a/72cen058.html ). A 2-to-1 tangent ogive nose cone for the #7 body tube, if it had a pointed (un-rounded) tip, would be 1.518" long from base to tip. Since the PNC-70 is 1.5" long, and has a rounded tip (if memory serves, the radius of its tip is ~3/16" to ~1/8" or so), its length--if its tip wasn't rounded, but was "allowed" to come to a sharp tip--would be somewhat more than 1.518". In other words, the PNC-70 isn't a 2-to-1 ogive, but is a longer ogive--perhaps 2.25-to-1 or 2.5-to-1, or some other ratio "in that neighborhood." Here (see: http://www.google.com/search?source...1.0.XVcuZ0ETB5c ) are several websites that show how tangent ogive nose cones (and secant ogive nose cones--the Bristol Aerojet Skua and Petrel [see: https://hu.wikipedia.org/wiki/Petrel and http://www.astronautix.com/p/petrel.html ] and the Honest John had secant ogive nose cones [the Honest John's was a "super-caliber" one]) are constructed geometrically; the Wikipedia article shows how both ogive nose cone types are constructed geometrically.

I hope this information will be helpful (and hopefully someone has a PNC-70 handy to measure, or photograph next to a ruler).

Based on these observations I have created a blunted tangent ogive PNC-70 design. Since I don't have a good drawing or actual PNC-70 I can't be sure I got the shape correct. It is very easy for me to create and modify these shapes since I know a shortcut and don't need to use a CAD program to generate the files I use for my 3D printers.

Thank you--that sounds intriguing!

What did you think of the 3D printed PNC-70 nosecone I sent you?